Concerns about rises in prices of fossil fuels have prompted intense interest in the development of engineered microorganisms as attractive sources for the production of biofuel. Photosynthetic algae have been of considerable interest as a possible biofuel resource for decades. Diatoms are one of the most ecologically successful unicellular phytoplankton on the planet, being responsible for approximately 20% of global carbon fixation, representing a major participant in the marine food web. They are able to accumulate abundant amounts of lipid suitable for conversion to liquid fuels and because of their high potential to produce large quantities and varieties of lipids and good growth efficiencies, they are considered as one of the best classes of algae for renewable biofuel production (Kroth 2007; Saade and Bowler 2009).
Nevertheless, relatively little is known about lipid metabolism in these algae. Extensive knowledge on complex lipid metabolism pathways is gained mostly from studies of plant or animal models. Genetic engineering of diatoms lipid gene is indispensable to understand the complex lipid metabolism and improve lipid production. However, despite the recent publication of Thalassiosira pseudonana (Armbrust, Berges et al. 2004) and Phaeodactylum tricornutum genomes (Bowler, Allen et al. 2008), very few genetic tools to explore diatoms genetics are available at this time: annotations of the diatoms genomes remain essentially based on putative open reading frames without confirmation of actual gene function. For instance, the direct manipulation of target genes by homologous recombination has proven difficult and the generation of loss of function mutants by insertional or chemical mutagenesis is challenging in diatoms because they are diploid organisms. This considerably limits the use of these organisms for biofuel applications. One genetic engineering study has succeeded to increase the amount of lipid within diatom. However, this was made by random integration of two transgenes involved in lipid metabolism (Radakovits, Eduafo et al. 2011).